Device for generating a beam of ions of high velocity



se 't.'17 ,194.o. 1,215,155

HARTMUT ESRAEL KALLMANN, FORMERLY KNOWN AS HARTMUT KALLMANN; ET AL DEVICE FOR GENERATING A BEAM 0F IONS OFHIGH VELOCITY Filed Feb. 10. 1939 Patented Sept. 17, 1940 UNITED STATES DEVICE FOR GENERATING A BEAM OF IONS OF HIGH VELOCITY Hartmut Israel Kallmann, formerly known as Hartmut Kallmann, Berlin-Charlottenburg, and Ernst Kuhn, Berlin, Germany, assignors to I. G. Farbenindustrie Aktiengesellschaft Application February 10, 1939, Serial No. 255,754

In Germany February 12, 1938 2 Claims.

In order to obtain an intense beam of ions of high velocity it has already been suggested to accelerate negative ions originating from a source of ions or obtained by transformation from positive ions by means of an electric field, then to transform said negative ions into positive ions and to accelerate further these positive ions by means of an electric field, whereafter they are collected. In the suggested arrangement the electrode within which the transformation of the said negative ions into positive ions takes place and which has a high positive potential relative to the source of the negative ions and to the collecting electrode,'is introduced into the vacuum by means of an insulating bushing.

At the potentials usually used it is diflicult to prevent sparkor flash-over by an extension of the insulating member. The reason therefore may be that the lead, which bears the high potential electrode is concentrically carried through the insulator.

In this way those parts of the insulator which are on one of their sides in contact with the earthed metal part and are on their other side located just opposite the lead that bears the high potential are subjected to a very great electrical stress.

These disadvantages are avoided in the present invention. The source of the negative ions, on the one hand, and the collecting electrode, on the other hand, respectively, are each separated by an insulating tube from the electrode serving for the transformation of the negative ions. This electrode itself is so designed that the two spaces enclosed by the insulating tubes communicate with one another preferably through the channel in which the transformation of the negative ions takes place. With this arrangement there is at the places of contact between the insulators and the metallic parts a considerably lower fieldstrength than with the above-mentioned former proposal.

The improved arrangement forming the subject-matter of this invention operates therefore, reliably with considerably higher potentials, and it is, besides, possible to obtain a more uniform distribution of the potential by subdividing the insulators and inserting in known manner metalelectrodes between the portions of the insulators and thereby to considerably increase the sparkor flash-over potential.

The invention is illustrated diagrammatically and byway of example on the accompanying drawing on which a preferred constructional form is shown in longitudinal section.

The positive ions produced in the source of ions I enter into the passage 2 and are transformed therein into negative ions, before theyenter into the discharge space. The beam 4 of I negative ions is accelerated by the field existing 5 between the exit-aperture 2 and the positively charged high-potential electrode 5. The ions. pass through the channel 6 of this electrode, into which channel gas is continually introduced through the pipe 1, so that the pressure in the 10 channel 6 is higher than in the space 3 of the device, which is evacuated by a pump (not shown) connected at 8.

In case of need, a pump for lowering the gas pressure can be provided also on the side where there is the source of the negative ions,

The negative ions are transformed to positive ions in the channel 5 of the high-potential electrode, and are then again accelerated by the field existing between the electrode 5 and the collecting electrode 9, so that they impinge with a very high speed upon the substance to be irradiated. The two metal disks [3 which are connected with the earthed parts of the device are, according to this invention, separated from the electrode 5 by the tube II which consists of an insulating material. In order to avoid sparkingor flashing-over along the outer surface a protection ring i2 is provided at the electrode carrying the high potential. It is, under circumstances, advantageous to provide annular bodies, such as [4, also at the earthed metal disks, and in a similar manner also the metallic members I5 and I6 may be provided with rings H and I8 for protection against glowor corona-discharge. The metallic parts l5 and 16 serving as subdividing members may be connected to a source of current for the purpose of providing a certain definite potential. In some cases, however, the desired. uniform potential distribution can be attained also by a suitable selection of the capacities of said parts relative to the adjacent parts.

We claim:

1. A device for generating a beam of ions of high velocity, comprising a source of negative ions, a converting electrode spaced from said source and providing means for accelerating negative ions from said source and for converting accelerated negative ions into positive ions, a col- 50 lecting electrode spaced from said converting electrode and providing means for accelerating the positive ions, and annular insulator members separating the source of negative ions from the converting electrode and said electrode from the 55 collecting electrode and forming a casing surrounding the path of travel of said ions.

.2. A device as defined in claim 1 including metallic members positioned between the source of negative ions and the converting electrode and between said electrode and the collecting electrode and separating each of said annular insulator members into at least two sections, said metallic members being perforated in the path of travel of said ions.

HARTMUT ISRAEL KALLMANN, Formerly known as Hartmut Kallma'rm.

' ERNST KUHN. i 

